RiotEmbed.js Coding Going Well

I’ve done more on riotEmbed today. Developed a system for hash code checking any scripts dynamically loaded. This should stop injection of just any code. There is also some removal of semantic and syntax errors based on ‘this’ and ‘call’, and some confusion between JSON, and JS which can contain roughly JSON, where ‘x: function()’ and ‘function x()’ are not quite the same.

I’ll do some planing of DB schema tomorrow …

The following link is a QUnit testing file I set up, which does no real tests yet, but is good for browser code testing, and much easier than the convoluted Travis CI virtual machine excess.

I’ve added in a dictionary acceleration method to the LZW, and called it PON (Packed Object Notation), which is only really effective when used after a BWT as in the pack method. Also some Unicode compression was added, which users of local 64 character sets will like. This leaves a final point in the compression layer of UCS-2 to UTF-8 conversion at the XmlHttpRequest boundary. By default this uses a text interface, and so the 16 bit characters native to JavaScript strings, are UTF-8 encoded and decoded at the eventual net octet streaming. As the PON is expected to be large (when compression is really needed) compared to any other uncompressed JSON, there is an argument to serialize for high dictionary codes (doubling of uncompressed JSON size, and almost a third of PON size), or post UTF to apply SUTF coding (cutting one third off compressed PON without affecting uncompressed JSON). The disadvantage to this is on the server side. The PON is the same, but the uncompressed JSON part will need an encoding and decoding function pair, and hence consume computational and memory buffer resources on the server.

As the aim of this compression layer is to remove load off the server, this is something to think about. The PON itself will not need that encoding taking off or putting on. As much of the uncompressed JSON part will be for SQL where clauses, and as indexes for arrays, the server can be considered ignorant of SUTF, as long as all literals used in the PHP script are ASCII. This is likely for all JSON keys, and literal values. So the second option on the client side of SUTF of the UTF would be effective. Some would say put Gzip on the server, but that would be more server load, which is to be avoided for scaling. I wonder if SUTF was written to accept use of the UInt8Array type?

Some hindsight analysis shows the one third gain is not likely to be realized except with highly redundant data. More realistic data has a wider than 64 dictionary code spread, and the middle byte of a UTF-8 is the easiest one to drop on repeats. The first byte contains the length indication, and as such the code would become much more complex to drop the high page bits, by juggling the lower four bits (0 to 3) in byte two for the lower four bits of byte one. Possibly a self inverse function … Implemented (no testing yet). The exact nature of JSON input to the pack function is next on the list client side, with the corresponding server side requirements of maintaining a searchable store, and distribution replication consistency.

The code spread is now 1024 symbols (maintaining easy decode and ASCII preservation), as anything larger would affect bits four and five in byte two and change the one third saving on three byte UTF-8 code points. There are 2048 dictionary codes before this compression is even used, and so only applies for larger inputs. As the dictionary codes are slightly super linear, I did have an idea to normalize them by subtracting a linear growth overtime, and then “invert the negative bulges” where lower and hence shorter dictionary codes were abnormal to the code growth trend. This is not applicable though as not enough information is easily available in a compressed stream to recover the coding. Well at least it gives something for gzip to have a crack at for those who want to burden the server.

Author: Jacko

Technical. Well is mass information conservation the reason for dark energy via uncertain geometry and photon exchange? Is dark matter conservation of acceleration with a gradient field heavy graviton? Does the KODEK work yet?
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